[Test] Add unit test to verify that cluster alarms have the expected settings.

[gmarciani]

Description of changes

Add unit test to verify that cluster alarms have the expected settings.
Before this change we were only testing the existence of the alarms and their type, but not the actual settings.
This is just an improvement of test coverage without any change to source code.

Why now?

1. Boy scout rule: while working on a task related to alarms, I noticed that our unit test was poor. Such limitation led us to cover the settings of alarms through integ tests rather than unit test.
2. Having this unit test in place increase our confidence around a refactoring that we are going to do in [Observability] Alarm on clustermgtd not running #7209

Tests

• Unit tests

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.